Based on a multimethod study that centers on interviews with over 30 conservationists, field biologists, ecologists, paleontologists and over 3 years of my fieldwork on urban beaches in the New York City area, the Florida Keys, and international conferences, Catch and Release explores the interspecies relationships between humans and horseshoe crabs—our multiple sites of entanglement and enmeshment as we both come to matter. As I show, crabs and humans make each other in particular ways. Humans have literally harvested the life out of horseshoe crabs for multiple purposes; we interpret them for understanding geologic time, we bleed them for biomedical applications, we collect them for agricultural fertilizer, we eat them as delicacies, we rescue them for conservation, we capture them as bait, we categorize them as Endangered. In contrast, the crabs make humans matter by revealing our species vulnerability to endotoxins, offering opportunities for career opportunities and profiteering off of crab bodies, and fertilizing the soil of agricultural harvest for human food. In these acts of harvesting, I consider how horseshoe crabs and humans make meaning of events such as the Anthropocene (the epoch of geologic time that attributes climate change and species decline to human activities), global warming, and biomedical innovation.